Composition and process for treating the surface of aluminiferous metals

ABSTRACT

A surface of aluminiferous metal is brought into contact at 30° C. to 65° C. for 5 to 60 seconds with a surface treatment bath with a pH of 2.0 to 6.5 that contains phosphate ion, condensed phosphate ion, and a water soluble polymer in the following weight proportions: 1-30: 0.1-10: 0.2-20. This is followed by a water rinse and drying by heating. The water soluble polymer has a chemical structure conforming with formula (I): ##STR1## in which (i) each of X 1  and X 2  represents a hydrogen atom, a C 1  to C 5  alkyl group, or a C 1  to C 5  hydroxyalkyl group; (ii) each of Y 1  and Y 2  represents a hydrogen atom or a moiety &#34;Z&#34; that conforms to formula (II) or (III): ##STR2## wherein each of R 1 , R 2 , R 3 , R 4 , and R 5  represents a C 1  to C 10  alkyl group or a C 1  to C 10  hydroxyalkyl group; (iii) the average value for the number of Z moieties substituted on each phenyl ring in the polymer molecule is from 0.2 to 1.0; (iv) n is an integer with a value from 2 to 50; and (v) each polymer molecule contains at least one Z moiety.

TECHNICAL FIELD

This invention relates to a novel composition and method for treatingthe surface of aluminiferous metals in order thereby to provide suchsurfaces, prior to their being painted, with an excellent corrosionresistance and paint adherence. The invention may be effectivelyapplied, inter alia, to the surface treatment of drawn-and-ironed(hereinafter usually abbreviated "DI") aluminum cans. When applied tothe DI aluminum cans fabricated by the drawing-and-ironing of aluminumalloy sheet, the surface treatment composition and method according tothe present invention are particularly effective in providing thesurface of such cans, prior to the painting or printing thereof, with anexcellent corrosion resistance and paint adherence and also with theexcellent slideability required for smooth conveyor transport of the can(abbreviated below simply as "slideability").

BACKGROUND ART

Liquid compositions, which hereinafter are often called "baths" forbrevity, even though they may be used by spraying or other methods ofestablishing intact than immersion, that are useful for treating thesurface of aluminiferous metals, defined as aluminum and its alloys thatcontain at least 45% by weight of aluminum, may be broadly classifiedinto chromate-type treatment baths and non-chromate-type treatmentbaths. The chromate-type surface treatment baths typically are dividedinto chromic acid chromate conversion treatment baths and phosphoricacid chromate conversion treatment baths. Chromic acid chromateconversion treatment baths were first used in about 1950 and are stillin wide use at present for the surface treatment of, for example, heatexchanger fins and the like. Chromic acid chromate conversion treatmentbaths contain chromic acid (CrO₃) and hydrofluoric acid (HF) as theiressential components and may also contain a invention accelerator. Thesebaths from a coating that contains small amounts of hexavalent chromium.The phosphoric acid chromate conversion treatment bath was invented in1945 (see U.S. Pat. No. 2,438,877). This conversion treatment bathcontains chromic acid (CrO₃), phosphoric acid (H₃ PO₄), and hydrofluoricacid (HF) as its essential components. The main component in the coatingproduced by this bath is hydrated chromium phosphate (CrPO₄.4H₂ O).Since this conversion coating does not contain hexavalent chromium, thisbath is still in wide use at present as, for example, a paint undercoattreatment for the lid and body of beverage cans.

The treatment bath taught in Japanese Patent Application Laid Open Kokaior Unexamined! Number Sho 52-131937 131,937/1977! is typical of thenon-chromate-type conversion treatment baths. This treatment bath is anacidic (pH=approximately 1.0 to 4.0) waterborne coating solution thatcontains phosphate, fluoride, and zirconium or titanium or theircompounds. Treatment of aluminiferous metal surfaces with thisnon-chromate-type conversion treatment bath produces thereon aconversion film whose main component is zirconium and/or titanium oxide.The absence of hexavalent chromium is one advantage associated with thenon-chromate-type conversion treatment baths; however, the conversioncoatings produced by them in many instances exhibit a corrosionresistance and paint adherence that is inferior to those of the coatingsgenerated by chromate-type conversion treatment baths. Moreover, bothchromate-type and non-chromate-type conversion treatment baths containfluorine, which conflicts with the contemporary desire, prompted byenvironmental concerns, for the practical implementation offluorine-free surface treatment baths.

The use of water-soluble resins in surface treatment baths and methodsintended to provide aluminiferous metals with corrosion resistance andpaint adherence is described, for example, in Japanese PatentApplication Laid Open Kokai or Unexamined! Numbers Sho 61-9136991,369/1986! and Hei 1-172406 172,406/1989!, Hei 1-177379 177,379/1989!,Hei 1-177380 177,380/1989!, Hei 2-608 608/1990!, and Hei 2-609609/1990!. In these examples of the prior art surface treatment bathsand methods, the metal surface is treated with a solution containing aderivative of a polyhydric phenol compound. However, the formation of anacceptably stable resin-containing coating on the aluminiferous metalsurface sometimes is highly problematic with these prior art methods,and they do not always provide an acceptable performance (corrosionresistance). The invention described in Japanese Patent Application LaidOpen Kokai or Unexamined! Number Hei 4-66671 66,671/1992! constitutes animprovement to treatment methods that use polyhydric phenol derivatives,but even in this case the problem of an unsatisfactory adherencesometimes arises.

The surface of DI aluminum cans is at present treated mainly with theabove-described phosphoric acid chromate surface treatment baths andzirconium-containing non-chromate surface treatment baths. The outsidebottom surface of DI aluminum cans is not painted, but is subjected tohigh-temperature sterilization. If its corrosion resistance is poor, thealuminum will become oxidized at this point and a blackeningdiscoloration will occur, a phenomenon which is generally known as"blackening". In order to prevent blackening, the coating produced bysurface treatment must itself, even when unpainted, exhibit a highcorrosion resistance.

Turning to another issue, a high friction coefficient for the can'sexterior surface will cause the can surface to have a poor slideabilityduring the conveyor transport that occurs in the can fabrication andfinishing processes. This will cause the can to tip over, which willobstruct the transport process. Can transportability is a particularconcern with regard to transport to the printer. Thus, there is demandin the can fabrication industry for a lowering of the static frictioncoefficient of the can's exterior surface, which, however, must beachieved without adversely affecting the adherence of the paint or inkwhich will be coated on the can. The invention disclosed in JapanesePatent Application Laid Open Kokai or Unexamined! Number Sho 64-8529285,292/1989! is an example of a method directed to improving thisslideability. This invention relates to a surface treatment agent formetal cans, wherein said surface treatment agent contains water-solubleorganic substance selected from phosphate esters, alcohols, monovalentand polyvalent fatty acids, fatty acid derivatives, and mixtures of thepreceding. While this method does serve to increase the slideability ofaluminum cans, it affords no improvement in corrosion resistance orpaint adherence.

The invention described in Japanese Patent Application Laid Open Kokaior Unexamined! Number Hei 5-239434 239,434/1993! is another methoddirected to improving the slideability of aluminum cans. This inventionis characterized by the use of phosphate esters. This method does yieldan improved slideability, but again it affords no improvement incorrosion resistance or paint adherence.

DISCLOSURE OF THE INVENTION Problems to Be Solved by the Invention

The present invention is directed to solving the problems describedabove for the prior art. In specific terms, the present inventionintroduces a composition and method for treating the surface ofaluminiferous metal which are able to provide the surface ofaluminiferous metal with an excellent corrosion resistance and paintadherence. When applied in particular to DI aluminum cans, saidcomposition and method impart thereto an excellent slideability incombination with an excellent corrosion resistance and paint adherence.

Details of the Invention, Including Preferred Embodiments Thereof

It has been found that the problems described above for the prior artcan be solved through the application of a specific type of surfacetreatment bath that is prepared using a surface treatment compositioncontaining specific phosphate ions, condensed phosphate ions, andwater-soluble polymers with a specific structure. It was found that theapplication of this surface treatment bath to the surface ofaluminiferous metal will form thereon a very corrosion-resistant andhighly paint-adherent resin-containing coating. It was also found thatapplication of said bath to DI aluminum cans forms thereon aresin-containing coating that exhibits an improved slideability inaddition to an excellent corrosion resistance and paint adherence. Theinvention was achieved based on these discoveries.

A composition according to the present invention for treating thesurface of aluminiferous metal characteristically comprises, preferablyconsists essentially of, or more preferably consists of, water and, inparts by weight:

(A) from 1 to 30 parts of phosphate ions;

(B) from 0.1 to 10 parts of condensed phosphate ions; and (C) from 0.1to 20 parts of water-soluble polymer conforming with the followinggeneral formula (I) ##STR3## in which each of X¹ and X² independently ofeach other and independently from one unit of the polymer, asrepresented by formula (I) above with the brackets and the subscript nomitted, to another unit of the polymer represents a hydrogen atom, a C₁to C₅ alkyl group, or a C₁ to C₅ hydroxyalkyl group; each of Y¹ and Y²independently of one another and independently for each unit of thepolymer represents a hydrogen atom or a moiety "Z" which conforms to oneof the following formulas (II) and (III): ##STR4## wherein each of R¹,R², R³, R⁴, and R⁵ in formulas (II) and (III) independently represents aC₁ to C₁₀ alkyl group or a C₁ to C₁₀ hydroxyalkyl group; the moiety Zbonded to any single phenyl ring in the polymer molecule may beidentical to or may differ from the moiety Z bonded to any other phenylring in the polymer molecule; the average value for the number of Zmoieties substituted on each phenyl ring in the polymer molecule is from0.2 to 1.0; n, which may be referred to hereinafter as "the averagedegree of polymerization", has a value from 2 to 50; and each polymermolecule (I) must contain at least one Z moiety-substituted phenyl ring.This average value for the number of Z moieties substituted on eachphenyl ring in the polymer molecules of total component (C) ishereinafter referred to as the average value for Z moiety substitution.

Compositions according to the invention as described above may be eitherworking compositions, suitable for directly treating aluminiferous metalsubstrates, or they may be concentrate compositions, which are usefulfor preparing working compositions, usually by dilution of theconcentrate compositions with water, and optionally, adjustment of thepH of the resulting working composition.

A method according to the present invention for treating the surface ofaluminiferous metal characteristically comprises contacting the surfaceof aluminiferous metal with a surface treatment bath containing theabove-described surface treatment composition according to the presentinvention, then rinsing the treated surface with water, and subsequentlydrying the surface by heating. Independently, in a method according tothe present invention, the bath preferably has a pH value of 6.5 orless, the total time of contacting the metal to be treated preferably isfrom 5 to 60 seconds, and the temperature during its contact with thealuminiferous metal being treated preferably is from 30° C. to 65° C.The reactivity of the bath may be insufficient below 30° C., preventingthe formation of a good-quality film. While a good-quality coating isformed at temperatures above 65° C., the higher energy costs for heatingmake such temperatures economically undesirable. Coating formation maybe inadequate and a highly corrosion-resistant coating may not beproduced when the immersion time is less than 5 seconds. Long immersiontimes in excess of 60 seconds usually produce no additional improvementsin performance and are disfavored because of their added expense.

The surface treatment method according to the present invention may beimplemented by immersing the aluminiferous metal, preferably for 5 to 60seconds, in the above-described surface treatment bath. The surfacetreatment method according to the present invention may also beimplemented by spraying the above-described surface treatment bath ontothe surface of the aluminiferous metal, preferably at least twice, andpreferably with an nonspray interval of from 2 to 5 seconds between eachperiod of continuous spraying and the next period of continuous sprayingif there is one. The occurrence of the pH increase in the vicinity ofthe interface with the surface, which is required for proper coatingformation, is less reliable when spray treatment is carried out bycontinuously spraying the bath, and in some cases a satisfactory filmformation will not occur. it is for this reason that use of anintermittent spray is preferred. The total of the spray and nonsprayinterval time periods preferably is from 5 to 60 seconds. The reactionmay be inadequate and a highly corrosion-resistant coating may not beproduced when the total contact time is less than 5 seconds. Lengthytotal contact times in excess of 60 seconds usually produce noadditional improvements in performance and are more expensive.

A surface treatment composition according to the present invention is anacidic aqueous solution whose essential ingredients are phosphate ion,condensed phosphate ion, and water-soluble polymer with theabove-specified chemical structure.

Phosphoric acid (H₃ PO₄), sodium phosphate (Na₃ PO₄), and the like canbe used as the source of the phosphate ion in the surface treatmentcomposition according to the present invention. The phosphate ioncontent in the above-described formulation ranges from 1 to 30 parts byweight (hereinafter often abbreviated "pbw"), while the preferred rangeis from 1 to 5 pbw. Reaction between the surface treatment bath and themetal surface will be insufficient and film formation often will beinadequate when the phosphate ions content in the above-describedformulation is less than 1 pbw. While a good-quality film is formed withmore than 30 pbw of phosphate ions, the high cost of the resultingtreatment bath makes such levels economically undesirable.

The condensed phosphate ions used in the present invention conform tothe general chemical formula H.sub.(p+1-q) P_(p) O.sub.(3p+1)^(-q),where p represents a positive integer that is 2 or greater and qrepresents a positive integer that is from 1 to (p+1); examples arepyrophosphate ions, tripolyphosphate ions, tetrapolyphosphate ions, andthe like. Either the condensed phosphoric acid or its neutral or acidsalt can be used as the condensed phosphate ion source for the surfacetreatment composition according to the present invention. For example,any of pyrophosphoric acid (H₄ P₂ O₇), disodium diacidpyrophosphate (Na₂H₂ P₂ O₇), trisodium acidpyrophosphate (Na₃ HP₂ O₇), and tetrasodiumpyrophosphate (Na₄ P₂ O₇), can be used as the source of thepyrophosphate ions. The condensed phosphate ions content in theabove-described formulation for the surface treatment compositionaccording to the present invention, measured as its stoichiometricequivalent of completely ionized condensed phosphate anions conformingto the formula P_(p) O.sub.(3p+1)⁻(p+2), where p and q have the samemeanings as above, ranges from 0.1 to 10 pbw, while the preferred rangeis from 0.5 to 3.0 pbw. Surface treatment baths prepared using less than0.1 pbw condensed phosphate ion in the above-described formulationusually have only a weak etching activity and provide inadequate filmformation. On the other hand, at more than 10 pbw the etching activitygenerated by the resulting surface treatment bath is too strong, so thatthe film-forming reactions are inhibited.

Polymer according to formula (I) with n less than 2 yields only aninsufficient improvement in the corrosion resistance of the resultingsurface coating. The stability of the corresponding surface treatmentcomposition and surface treatment bath is sometimes inadequate andpractical problems often ensue in the case of polymer (I) with n greaterthan 50.

The presence of 6 or more carbons in the alkyl and hydroxyalkyl groupsrepresented by X¹ and X² in formula (I) causes the resulting polymermolecule to be bulky and produces steric hindrance. This usuallyinterferes with the formation of the fine, dense coatings that exhibitexcellent corrosion resistance.

Polymer (I) contains the Z moiety as a substituent, and the averagevalue for Z moiety substitution for each phenyl ring in the polymermolecule must range from 0.2 to 1.0. As an example, in a polymer withn=10 that has 20 phenyl rings, if only 10 of these 20 phenyl rings aresubstituted by one Z moiety each, the average value for Z moietysubstitution for this polymer is then calculated as follows:(1×10)/20=0.5.

The polymer usually is insufficiently water soluble when the averagevalue for Z moiety substitution is below 0.2; this results in aninsufficiently stable surface treatment concentrate and/or surfacetreatment bath. When, on the other hand, the average value for Z moietysubstitution exceeds 1.0 (substitution of a phenyl ring by 2 or moremoieties Z), the resulting polymer becomes so soluble in water thatformation of an adequately protective surface film is impeded.

The alkyl and hydroxyalkyl moieties encompassed by R¹, R², R³, R⁴, andR⁵ in formulas (II) and (III) should contain from 1 to 10 carbon atomseach. The polymer molecule becomes bulky when this number of carbonsexceeds 10; this results in a coarse coating and thereby in aninsufficient improvement in the corrosion resistance.

The content of water-soluble polymer (I) in the above-describedformulation for the surface treatment composition according to thepresent invention ranges from 0.1 to 20 pbw, while the range from 0.5 to5 pbw is preferred. The formation of a coating on the metal surface bythe corresponding surface treatment bath often becomes quite problematicwhen the content of the water-soluble polymer in the above-describedformulation is below 0.1 pbw. Values above 20 pbw are economicallyundesirable due to the increased cost of the surface treatmentcomposition and surface treatment method.

The pH of the surface treatment composition according to the presentinvention is not narrowly restricted, but adjustment of the pH to valuesno greater than 6.5, more preferably also not less than 2.0, isgenerally preferred.

The method according to the present invention is implemented by thepreparation of a working surface treatment bath using theabove-described surface treatment composition (generally by dilution ofa concentrate with water). The pH of the working surface treatment bathat this point is adjusted if necessary to values no greater than 6.5 andpreferably to 2.0 to 6.5.

The polymer conforming to formula (I) in the surface treatment bath hasa pronounced tendency to deposit or precipitate at a surface treatmentbath pH above 6.5; this results in an unsatisfactory stability andservice life for the treatment bath. When the pH is below 2.0, thesurface treatment bath may etch the metal surface too severely, whichcan impair formation of the surface coating. The pH of the surfacetreatment bath may be adjusted using an acid, e.g., phosphoric acid,nitric acid, hydrochloric acid, and the like, or by using alkali, e.g.,sodium hydroxide, sodium carbonate, ammonium hydroxide, and the like.Hydrofluoric acid may be used to adjust the pH when waste watertreatment presents no problems.

When the aluminum ions eluted from the aluminiferous metal being treatedaccording to the invention mixes into the surface treatment bath, aprecipitate may be produced in some cases due to the formation of acomplex between polymer (I) and the aluminum ions. An aluminumsequestrant is preferably added to the treatment bath in such cases.Suitable as said aluminum sequestrant are, for example, ethylene diaminetetraacetic acid, Cy-DTA, triethanolamine, gluconic acid, heptogluconicacid, oxalic acid, tartaric acid, malic acid, and organophosphonicacids, but the particular sequestrant selection is not critical.Hydrofluoric acid may be used as the sequestrant when it presents noproblems for waste water treatment.

A process according to the present invention preferably is performed bycontacting the surface of aluminiferous metal with a surface treatmentbath--prepared as described above--at 30° C. to 65° C. for a total of 5to 60 seconds. The process then continues with a water rinse of the filmformed on the metal surface and drying by heating.

Problems with the coating can occur due to foaming of the surfacetreatment bath when a spray treatment is used. The generation of foamand the intensity of foaming strongly depend on the type of sprayequipment and the spraying conditions, and a defoamer is preferablyadded to the surface treatment bath when a foaming problem cannot besatisfactorily resolved by changes to the spray equipment and/orconditions. Such factors as the type and dispensing level of thedefoamer are not critical, provided that they do not impair the paintadherence of the resulting coating.

A preferred method of preparation of a surface treatment compositionaccording to the present invention will now be briefly summarized. Toprepare the surface treatment composition, the phosphate ions andcondensed phosphate ions are first made up in the above-describedproportions and dissolved with thorough stirring in the required amountof water according to the preceding specifications. When the pH of theresulting solution exceeds 7, it is adjusted to less than or equal to 7using a suitable acid as described above. The water soluble resinspecified by the invention is then added while stirring and completelydissolved, and the pH is adjusted to less than or equal to 6.5 asdescribed above.

The coating formed on the surface of aluminiferous metal will now alsobe briefly discussed. The coating formed by the surface treatment bathaccording to the present invention is an organic-inorganic compositecoating whose main components are phosphate salt and polymer (I).Etching of the metal surface by the phosphate ions and condensedphosphate ions causes a local increase in pH to occur at the interface;this results in deposition of phosphate salt on the metal surface. Inaddition, the chelating activity of the amino group in polymer (I) mayresult in the formation of a coordination compound with the freshsubstrate surface exposed by etching. The presence of condensedphosphate ions in the surface treatment bath is believed to promoteformation of the polymer-metal coordination compound and thereby makepossible stable formation of the organic-inorganic composite coating onthe surface over a broad pH range.

An additional polymerization of the polymer present on the surface canbe induced by heating the surface coating after its formation. Inspecific cases where an elevated corrosion resistance is required, thecoating is preferably heated in order to produce a higher molecularweight for the polymer on the surface. Suitable heating conditions forthis purpose are at least 1 minute and at least 200° C.

Aluminiferous metal substrates that may be subjected to the methodaccording to the present invention comprise, for example, the sheet,bar, tube, wire, and like shapes, of aluminum and its alloys, e.g.,aluminum-manganese alloys, aluminum-magnesium alloys, aluminum-siliconalloys, and the like. There are absolutely no limitations on thedimensions or shape of the aluminiferous metal.

The polymer composition according to the present invention may contain apreservative or antimold agent. These function to inhibit putrefactionor mold growth when the surface treatment bath is used or stored at lowtemperatures. Hydrogen peroxide is a specific example in this regard.

The following is a short discussion of further details of a process oftreating the surface of aluminiferous metal using the surface treatmentbath according to the present invention. The process steps outlinedbelow are a preferred example of application of the surface treatmentbath according to the present invention.

(1) Surface cleaning: degreasing--an acidic, alkaline, or solvent-baseddegreaser may be used.

(2) Water rinse

(3) Film-forming treatment (surface treatment method according to thepresent invention)

(4) Water rinse

(5) Rinse with de-ionized water

(6) Drying

The invention is illustrated in greater detail below through workingexamples, and its benefits may be further appreciated by contrast withthe comparison examples. The individual surface treatment bathcomponents and surface treatment methods are respectively described inthe working and comparative examples.

EXAMPLES Evaluation Methods

(1) Corrosion resistance

The corrosion resistance of the unpainted parts of the DI aluminum cans(resistance to blackening by boiling water) was evaluated based on thedegree of discoloration (blackening) after immersion of treated DIaluminum cans in boiling tap water for 30 minutes. The results of thistest are reported on the following scale:

+: no blackening

×: partial blackening

××: blackening over entire surface

(2) Paint adherence

The paint adherence was tested as follows. The surface of the treatedcan was coated to a paint film thickness of 5 to 7 micrometers with anepoxy-urea can paint. This was followed by baking for 4 minutes at 215°C. A 5 millimeter (hereinafter usually abbreviated "mm")×150 mm stripwas then cut from the painted can and hot-press bonded with polyamidefilm to give a test specimen. The test specimen thus prepared wassubjected to a 180° peel test, during which the peel strength wasmeasured. Higher peel strength values in this test are indicative of abetter paint adherence, and peel strength values equal to or greaterthan 4.0 kilograms-force per 5 millimeters of width (hereinafter usuallyabbreviated as "kgf/5 mm") are generally regarded as excellent from thestandpoint of practical applications.

(3) Slideability

The slideability was evaluated by measuring the static frictioncoefficient on the outside surface of the can. Lower values for thestatic friction coefficient are indicative of a better slideability, andvalues less than or equal to 1.0 are generally regarded as excellent.

Example 1

DI aluminum cans fabricated by the DI processing of A3004 aluminum alloysheet were cleaned by first degreasing with a 60-second spray at 75° C.of an 8% aqueous solution of PALKLIN™ 500 acidic degreaser manufacturedby Nihon Parkerizing Company, Limited and then rinsing with water. Thecleaned surface was subsequently sprayed with Surface Treatment Bath 1(composition given below) heated to 60° C. The spray treatment consistedof 3 sprays of 5 seconds each separated by 5 second intervals for atotal of 25 seconds. This was followed in order by rinsing with tapwater, spraying for 10 seconds with deionized water (with a resistivityof at least 3,000,000 ohm-cm), and drying in a hot-air drying oven at180° C. for 2 minutes.

Surface Treatment Bath 1

    ______________________________________                                        75% Aqueous phosphoric                                                                       10.0 g/L   (PO.sub.4.sup.-3 ions: 7.2 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         3.0 g/L    (P.sub.2 O.sub.7.sup.-4 ions: 1.2 g/L)              (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  2.0 g/L    (solids)                                            Polymer 1:                                                                    ______________________________________                                    

pH: 4.0 (adjusted with sodium hydroxide)

Balance: water

For Water-Soluble Polymer 1, n=5, X¹ and X² =hydrogen, Z=--CH₂ N(CH₃)₂in formula (I), and the average value for Z moiety substitution=0.25.

Example 2

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 20 seconds in Surface Treatment Bath2 (composition given below) heated to 60° C. This treatment was followedby rinsing with water and drying according to the procedure described inExample 1.

Surface Treatment Bath 2

    ______________________________________                                        75% Aqueous phosphoric                                                                       10.0 g/L   (PO.sub.4.sup.-3 ions: 7.2 g/L)                     acid (H.sub.3 PO.sub.4):                                                      sodium pyrophosphate                                                                         3.0 g/L    (P.sub.2 O.sub.7.sup.-4 ions: 1.2 g/L)              (Na.sub.4 P.sub.2 O.sub.7 10H.sub.2 O):                                       Water-Soluble  0.4 g/L    (solids)                                            Polymer 1:                                                                    ______________________________________                                    

pH: 3.0 (adjusted with sodium carbonate)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Example 3

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 60 seconds in Surface Treatment Bath3 (composition given below) heated to 35° C. This treatment was followedby rinsing with water and drying according to the procedure described inExample 1.

Surface Treatment Bath 3

    ______________________________________                                        75% Aqueous phosphoric                                                                       20.0 g/L   (PO.sub.4.sup.-3 ions: 14.4 g/L)                    acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         6.0 g/L    (P.sub.2 O.sub.7.sup.-4 ions: 2.4 g/L)              (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  8.0 g/L    (solids)                                            Polymer 1:                                                                    ______________________________________                                    

pH: 6.0 (adjusted with sodium hydroxide)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Example 4

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then sprayed with Surface Treatment Bath 4 (compositiongiven below) heated to 65° C. The spray treatment consisted of 3 sprays(6 seconds each) separated by intervals of 2 seconds (total of 22seconds). This treatment was followed by rinsing with water and dryingaccording to the procedure described in Example 1.

Surface Treatment Bath 4

    ______________________________________                                        75% Aqueous phosphoric                                                                       1.5 g/L   (PO.sub.4.sup.-3 ions: 1.1 g/L)                      acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         5.0 g/L   (P.sub.2 O.sub.7.sup.-4 ions: 2.0 g/L)               (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  4.0 g/L   (solids)                                             Polymer 1:                                                                    ______________________________________                                    

pH: 2.5 (adjusted with nitric acid)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Example 5

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 30 seconds in Surface Treatment Bath5 (composition given below) heated to 60° C. This treatment was followedby rinsing with water and drying according to the procedure described inExample 1.

Surface Treatment Bath 5

    ______________________________________                                        75% Aqueous phosphoric                                                                       30.0 g/L   (PO.sub.4.sup.-3 ions: 21.6 g/L)                    acid (H.sub.3 PO.sub.4):                                                      Sodium tripolyphosphate                                                                      1.2 g/L    (P.sub.3 O.sub.10.sup.-5 ions: 0.8 g/L)             (Na.sub.5 P.sub.3 O.sub.10):                                                  Water-Soluble  2.0 g/L    (solids)                                            Polymer 1:                                                                    ______________________________________                                    

pH: 3.5 (adjusted with sodium hydroxide)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Example 6

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then sprayed with Surface Treatment Bath 6 (compositiongiven below) heated to 60° C. The spray treatment consisted of 2 spraysof 5 seconds each separated by an interval of 5 seconds for a total of15 seconds). This treatment was followed by rinsing with water anddrying according to the procedure described in Example 1.

Surface Treatment Bath 6

    ______________________________________                                        75% Aqueous phosphoric                                                                       10.0 g/L   (PO.sub.4.sup.-3 ions: 7.2 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         3.0 g/L    (P.sub.2 O.sub.7.sup.-4 ions: 1.2 g/L)              (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  2.0 g/L    (solids)                                            Polymer 2:                                                                    ______________________________________                                    

pH: 5.0 (adjusted with sodium hydroxide)

Balance: water

For Water-Soluble Polymer 2, in formula (I), n=5, X¹ and X² =--C₂ H₅,and Z=--CH₂ N(CH₂ CH₂ OH)₂, and the average value for Z moietysubstitution=1.0.

Example 7

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 30 seconds in Surface Treatment Bath7 (composition given below) heated to 60° C. This treatment was followedby rinsing with water and drying according to the procedure described inExample 1.

Surface Treatment Bath 7

    ______________________________________                                        75% Aqueous phosphoric                                                                       10.0 g/L   (PO.sub.4.sup.-3 ions: 7.2 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         3.0 g/L    (P.sub.2 O.sub.7.sup.-4 ions: 1.2 g/L)              (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O)                                        Water-Soluble  2.0 g/L    (solids)                                            Polymer 3:                                                                    ______________________________________                                    

pH: 4.0 (adjusted with sodium hydroxide)

Balance: water

For Water-Soluble Polymer 3, in formula (I), n=2, X¹ and X² =--C₂ H₅,and Z=--CH₂ N(CH₂ CH₂ CH₂ OH)₂, and the average value for Z moietysubstitution=0.6.

Comparative Example 1

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then sprayed with Surface Treatment Bath 8 (compositiongiven below) heated to 60° C. The spray treatment consisted of 5 spraysof 4 seconds each separated by intervals of 5 seconds each, for a totalof 40 seconds. This treatment was followed by rinsing with water anddrying according to the procedure described in Example 1.

Surface Treatment Bath 8

    ______________________________________                                        75% Aqueous phosphoric                                                                       10.0 g/L   (PO.sub.4.sup.-3 ions: 7.2 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Water-Soluble   2.0 g/L   (solids)                                            Polymer 1:                                                                    ______________________________________                                    

pH: 3.0 (adjusted with sodium carbonate)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Comparative Example 2

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 30 seconds in Surface Treatment Bath9 (composition given below) heated to 60° C. This treatment was followedby rinsing with water and drying according to the procedure described inExample 1.

Surface Treatment Bath 9

    ______________________________________                                        75% Aqueous phosphoric                                                                       1.0 g/L   (PO.sub.4.sup.-3 ions: 0.72 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Water-Soluble  2.0 g/L   (solids)                                             Polymer 1:                                                                    ______________________________________                                    

pH: 7.0 (adjusted with sodium hydroxide)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Comparative Example 3

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 5 seconds in Surface Treatment Bath10 (composition given below) heated to 60° C. This treatment wasfollowed by rinsing with water and drying according to the proceduredescribed in Example 1.

Surface Treatment Bath 10

    ______________________________________                                        75% Aqueous phosphoric                                                                       10.0 g/L   (PO.sub.4.sup.-3 ions: 7.2 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         1.0 g/L    (P.sub.2 O.sub.7.sup.-4 ions: 0.4 g/L)              (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  0.05 g/L   (solids)                                            Polymer 1:                                                                    ______________________________________                                    

pH: 4.0 (adjusted with sodium carbonate)

Balance: water

Water-Soluble Polymer 1 was the same as described in Example 1.

Comparative Example 4

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 20 seconds in Surface Treatment Bath11 (composition given below) heated to 60° C. This treatment wasfollowed by rinsing with water and drying according to the proceduredescribed in Example 1.

Surface Treatment Bath 11

    ______________________________________                                        95% Aqueous sulfuric acid                                                                     2.0 g/L    (SO.sub.4.sup.-2 ions: 1.9 g/L)                    (H.sub.2 SO.sub.4):                                                           Sodium pyrophosphate                                                                          1.0 g/L    (P.sub.2 O.sub.7 ion: 0.4 g/L)                     (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble   0.05 g/L   (solids)                                           Polymer 1:                                                                    ______________________________________                                    

pH: 3.5 (adjusted with sodium carbonate)

Water-Soluble Polymer 1 was the same as described in Example 1.

Comparative Example 5

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 30 seconds in Surface Treatment Bath12 (composition given below) heated to 60° C. This treatment wasfollowed by rinsing with water and drying according to the proceduredescribed in Example 1.

Surface Treatment Bath 12

    ______________________________________                                        75% Aqueous phosphoric                                                                       1.0 g/L   (PO.sub.4.sup.-3 ions: 0.72 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         1.0 g/L   (P.sub.2 O.sub.7.sup.-4 ions: 0.4 g/L)               (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  2.0 g/L   (solids)                                             Polymer 4:                                                                    ______________________________________                                    

pH: 4.0 (adjusted with sodium hydroxide)

Balance: water

For Water-Soluble Polymer 4, in formula (I), n=5, X¹ and X² =--C₂ H₅,and Z=--CH₂ SO₃ H, and the average value for --CH₂ SO₃ Hsubstitution=0.6.

Comparative Example 6

The DI aluminum cans were cleaned according to the procedure describedin Example 1 and then immersed for 30 seconds in Surface Treatment Bath13 (composition given below) heated to 60° C. This treatment wasfollowed by rinsing with water and drying according to the proceduredescribed in Example 1.

Surface Treatment Bath 13 (surface treatment bath described in JapanesePatent Application Laid Open Kokai or Unexamined! Number Hei 4-66671)

    ______________________________________                                        75% Aqueous phosphoric                                                                       1.0 g/L   (PO.sub.4.sup.-3 ions: 0.72 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         1.0 g/L   (P.sub.2 O.sub.7.sup.-4 ions: 0.4 g/L)               (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  2.0 g/L   (solids)                                             Polymer 5:                                                                    ______________________________________                                    

pH: 4.0 (adjusted with sodium hydroxide)

Balance: water

Water-Soluble Polymer 5 had the following formula (IV): ##STR5##

Comparative Example 7

The DI aluminum cans were cleaned according to the procedure describedin Example I and then immersed for 30 seconds in Surface Treatment Bath14 (composition given below) heated to 60° C. This treatment wasfollowed by rinsing with water and drying according to the proceduredescribed in Example 1.

Surface Treatment Bath 14

    ______________________________________                                        75% Aqueous phosphoric                                                                       1.0 g/L   (PO.sub.4.sup.-3 ions: 0.72 g/L)                     acid (H.sub.3 PO.sub.4):                                                      Sodium pyrophosphate                                                                         1.0 g/L   (P.sub.2 O.sub.7.sup.-4 ions: O.4 g/L)               (Na.sub.4 P.sub.2 O.sub.7.10H.sub.2 O):                                       Water-Soluble  2.0 g/L   (solids)                                             Polymer 6:                                                                    ______________________________________                                    

pH: 4.0 (adjusted with sodium hydroxide)

Balance: water

Water-Soluble Polymer 6 had the following formula (V) (resin describedin Japanese Patent Application Laid Open Kokai or Unexamined! Number Hei2-608): ##STR6##

Comparative Example 8

The DI aluminum cans were cleaned according to the procedure de-DINE®404 non-chromate surface treatment agent, manufactured by NihonParkerizing Company, Limited, heated to 40° C. This spray treatmentconsisted of 3 sprays of 5 seconds each separated by 5 second intervalsfor a total of 25 seconds. This treatment was followed by rinsing withwater and drying according to the procedure described in Example 1.

The evaluation results for Examples 1 to 7 and Comparative Examples 1 to8 are reported in Table 1.

                  TABLE 1                                                         ______________________________________                                        Results of the Evaluations                                                    Example or Compar-                                                                         Blackening                                                                              Peel Strength,                                                                           Coefficient of                              ison Example Number                                                                        Resistance                                                                              kgf/5 mm   Static Friction                             ______________________________________                                        Example 1    +         4.0        0.9                                         Example 2    +         4.0        0.9                                         Example 3    +         4.0        0.9                                         Example 4    +         4.0        0.9                                         Example 5    +         4.0        0.9                                         Example 6    +         4.0        0.9                                         Example 7    +         4.0        0.9                                         Comparative Example 1                                                                      x         2.0        1.3                                         Comparative Example 2                                                                      x x       1.5        1.5                                         Comparative Example 3                                                                      x x       2.0        1.5                                         Comparative Example 4                                                                      x x       1.5        1.5                                         Comparative Example 5                                                                      x x       1.5        1.6                                         Comparative Example 6                                                                      +         2.0        1.1                                         Comparative Example 7                                                                      x x       1.5        1.6                                         Comparative Example 8                                                                      +         4.0        1.6                                         ______________________________________                                    

As the results in Table 1 make clear, Examples 1 to 7, which usedsurface treatment compositions and surface treatment methods accordingto the present invention, yielded surface-treated metals with anexcellent blackening resistance, excellent adherence, and excellentslideability. In contrast to this, satisfactory values could not besimultaneously obtained for all these properties (corrosion resistance,paint adherence, and slideability) in the case of the surface-treatedmetals afforded by surface treatment baths outside the scope of thepresent invention (Comparative Examples 1 to 8).

Benefits of the Invention

As the preceding description has made clear, the surface treatmentcomposition and surface treatment method according to the presentinvention can produce very corrosion-resistant and highly paint-adherentconversion coatings on the surface of aluminiferous metals prior to thepainting thereof. In particular, application of the surface treatmentcomposition according to the present invention to the treatment of DIaluminum cans results in the formation on the surface of DI aluminumcans prior to its painting or printing of a very corrosion-resistant andhighly paint-adherent film that also provides the excellent slideabilityrequired for smooth conveyor transport of the can. Since the surfacetreatment composition according to the present invention and the surfacetreatment bath used in the invention method do not contain chromium orfluorine, they have the excellent advantage of reducing the load onwaste water treatment.

The invention claimed is:
 1. An aqueous liquid composition for treatingthe surface of aluminiferous metals, either as such or after dilutionwith additional water, said composition comprising water and:(A) from 1to 30 pbw of phosphate ions; (B) from 0.1 to 10 pbw of condensedphosphate ions; and (C) from 0.1 to 20 pbw of water-soluble polymerconforming with the following general formula (I) ##STR7## in which (i)each of X¹ and X², independently of each other and independently fromone unit of the polymer, which is defined as a part of the polymer thatconforms with formula (I) above except that the brackets and thesubscript n are omitted, to another unit of the polymer, represents ahydrogen atom, a C₁ to C₅ alkyl group, or a C₁ to C₅ hydroxyalkyl group;(ii) each of Y¹ and Y², independently of one another and independentlyfrom one unit of the polymer to another, represents a hydrogen atom or amoiety "Z" that conforms to formula (II) or (III): ##STR8## wherein eachof R¹, R², R³, R⁴, and R⁵, independently of each other and independentlyfrom one unit of the polymer to another, represents a C₁ to C₁₀ alkylgroup or a C₁ to C₁₀ hydroxyalkyl group; (iii) the moiety Z bonded toany single phenyl ring in the polymer molecule may be identical to ormay differ from the moiety Z bonded to any other phenyl ring in thepolymer molecule; (iv) the average value for the number of Z moietiessubstituted on each phenyl ring in the polymer molecule is from 0.2 to1.0; (v) n is an integer with a value from 2 to 50; and (vi) eachpolymer molecule contains at least one Z moiety.
 2. A compositionaccording to claim 1, comprising from 1 to 5 pbw of phosphate ions, from0.5 to 3 pbw of condensed phosphate ions, and from 0.5 to 5 pbw of watersoluble polymer conforming with formula (I).
 3. A composition accordingto claim 2, having a pH value from 2.0 to 6.5 and comprising from 1 to30 g/L of phosphate ions, from 0.1 to 10 g/L of condensed phosphateions, and from 0.1 to 20 g/L of water soluble polymer conforming withformula (I).
 4. A composition according to claim 1, having a pH valuenot greater than 6.5 and comprising from 1 to 30 g/L of phosphate ions,from 0.1 to 10 g/L of condensed phosphate ions, and from 0.1 to 20 g/Lof water soluble polymer conforming with formula (I).
 5. A process fortreating a surface of aluminiferous metal, said process comprising stepsof:(I) contacting the surface of aluminiferous metal for from 5 to 60seconds at from 30° C. to 65° C. with a composition according to claim4; (II) after completion of step (I), separating the surface ofaluminiferous metal from contact with a composition according to claim 4and rinsing the surface with water; and (III) drying by heating thesurface of aluminiferous metal rinsed in step (II).
 6. A processaccording to claim 5, wherein step (I) is accomplished by immersing thealuminiferous metal surface in the composition.
 7. A process accordingto claim 5, wherein step (I) is accomplished by spraying the compositionon to the aluminiferous metal surface.
 8. A process according to claim7, wherein: the aluminiferous metal surface is sprayed at least twice;periods of contact by spraying are interrupted by nonspraying intervalsof from 2 to 5 seconds; and total time between completing the firstspraying and ending the last spraying is from 5 to 60 seconds.
 9. Aprocess for treating a surface of aluminiferous metal, said processcomprising steps of:(I) contacting the surface of aluminiferous metalfor from 5 to 60 seconds at from 30° C. to 65° C. with a compositionaccording to claim 3; (II) after completion of step (I), separating thesurface of aluminiferous metal from contact with a composition accordingto claim 3 and rinsing the surface with water; and (III) drying byheating the surface of aluminiferous metal rinsed in step (II).
 10. Aprocess according to claim 9, wherein step (I) is accomplished byimmersing the aluminiferous metal surface in the composition.
 11. Aprocess according to claim 10, wherein step (I) is accomplished byspraying the composition on to the aluminiferous metal surface.
 12. Aprocess according to claim 11, wherein: the aluminiferous metal surfaceis sprayed at least twice; periods of contact by spraying areinterrupted by nonspraying intervals of from 2 to 5 seconds; and totaltime between completing the first spraying and ending the last sprayingis from 5 to 60 seconds.